a couple of HS&F questions

I've recently set up a totaly new gaming rig and since I've never had to worry about CPU temperature too much becuase I've never had enough cash to get a fast enough processor these questions may sound a bit n00bish.

I normaly have my CPU (a Athlon XP1800+) running at a temperature of 36-39oC when I'm not doing too much but I checked it after a long gaming session (to make sure my GF3 worked ) and I noticed it had gone up to 50oC

Now my thinking is that 50oC is half boiling point and isn't good so should I be worried about it reaching this temperature and check my HS&F or is this normal and I'm just worrying over nothing?

Something else I was wonderign is that thermal grease for your HS&F is white right? The thing is that my HS&F came with thermal grease already on it that was pink and I'm wodering if I'm going to have to take it off and apply some that I've got lying arround. The HS&F is AMD approved so I thought that it would probably be ok but the fact that it was pink made me wonder whetehr it was ok.

Thanks for any help and thanks for putting up with these really n00bish questions